1. Field of the Invention
The present invention relates to a communication system including a communication terminal connectable to first and second communication networks, and a controller configured to control service provision to the communication terminal according to which one of the first and second communication networks the communication terminal is currently connected to. Moreover, the present invention also relates to a communication terminal and a controller in such a communication system.
2. Description of the Related Art
There has been known fixed mobile convergence (FMC) that allows a mobile terminal to establish communications with both a mobile phone network (hereinafter, called a “mobile network”) and a fixed telephone network (hereinafter, called a “fixed network”).
A mobile phone terminal that supports FMC (hereinafter, called a “FMC supported terminal”) communicates with the fixed network through an access point (hereinafter abbreviated as an “AP”) by use of short distance wireless communication techniques such as a wireless LAN and Bluetooth (registered trademark). A user can use a common telephone number for both connections of the FMC supported terminal to the fixed network and the mobile network.
When APs are installed, for example, for a home, one or multiple APs are usually Installed so as to have such a small-scale coverage that only the premises of the single home can be covered The FMC supported terminal is connected to the fixed network through the AP inside the premises, and is connected to the mobile network outside the premises. In a place where the FMC supported terminal can establish connections to both the fixed network and the mobile network, such as inside the premises, the FMC supported terminal preferentially establishes a connection to the fixed network.
In addition, in terms of charges for the FMC supported terminal, a fee for the mobile phone service is charged when the FMC supported terminal is connected to the mobile network, while a fee for the fixed telephone service is charged when the FMC supported terminal is connected to the fixed network. The connection fee for the fixed network is generally cheaper than that for the mobile network. For this reason, the most advantageous point for a user is that the user is charged only for the fixed network at home even while using a mobile phone terminal
When the FMC supported terminal is used, however, there is a case where communication quality good enough to enable the FMC supported terminal to establish voice communications through AP cannot be maintained even near the AP, that is, inside the premises, because an obstacle blocks or interference win radio waves or because the AP is busy. There are two countermeasures against a failure in obtaining such good enough communication quality between the FMC supported terminal and the AP: (1) maintaining a connection with low communication quality between the FMC supported terminal and the fixed network; and (2) switching the network connected to the FMC supported terminal, to the mobile network.
If the connection with low communication quality between the FMC supported terminal and the fixed network is maintained, a risk of disconnection increases. If the network connected to the FMC supported terminal is switched to the mobile network, the communication quality can be prevented from deteriorating, but the connection fee increases since the fee for the mobile network is charged. In this case, the user is charged for the mobile network, while using the terminal in a place supposed to be charged for the fixed network. As a result, the user may be discontent with this changing, so that the user may make a complaint.
A solution for this problem is to widen the coverage of the AP by increasing the transmission power of the AP. This solution, however, may deteriorate the communication quality in an adjacent home because the adjacent home is subject to interference waves as a result of an increase of the transmission power of the AP. Another solution is to increase the number of APs installed in a home. However, this solution has problems of requiring a larger amount of costs and causing interference among the APs.
As described above, user's convenience is reduced when the difficulty of establishing a connection to a desired communication network (fixed network) forces a terminal to be connected to another communication network (mobile network). This problem of reducing user's convenience occurs not only between the fixed network and the mobile network, but also between any arbitrary types of communication networks.